SD50 - water alarm advice

[meirriba]

The alarm went off. It alarms when the outer/lower seal is breached and seawater gets between the seals.

Do anyone has experience with this? the user manual says to go immediately to a boatyard for repair.
Has anyone experienced a malfunctioning of the sensor only (while seals are intact)?
Is the inner seal good enough to rely on it for another week or so?
Any other comment?

[HeinSdL]

I have the same saildrive. Alarm has never gone off but I did see some condensation inside on occasions (when removing the sensor to test it. Advisable to do this yearly.) I have also heard of false alarms with other people (alarm went off, but after rushing back to port, there wasn't a breach of the main seal).


In your situation I would go to the sensor (starboard side of saildrive, plastic plug with wires coming out at the base of the saildrive) and SLOWLY remove it (careful: use a large set of plyers and protect with a cloth to loosen it. It might be stuck you don't want to break it). If at any time water starts to gush out, screw back in and, indeed, get to port and on the dry asap. If the sensor comes out and is damp or there is water coming into the boat perhaps more slowly, then also go back to the port, but no immediate cause for alarm. If the sensor is dry then there is a problem elsewhere with the wiring.


I would under no circumstances rely on the upper seal to keep the water out on a sustainable basis. I would also not use the engine until the last moment if you discover the lower seal is gone.

[skipperpete]

Originally Posted by meirriba

The alarm went off. It alarms when the outer/lower seal is breached and seawater gets between the seals.

Do anyone has experience with this? the user manual says to go immediately to a boatyard for repair.
Has anyone experienced a malfunctioning of the sensor only (while seals are intact)?
Is the inner seal good enough to rely on it for another week or so?
Any other comment?

I'm assuming this is a Yanmar Saildrive.
A reasonable course of action would be to unscrew the sender very carefully and see if the void is in fact filled with water but be ready to screw it back in pronto if the outer diaphragm has failed. You might see the inner seal distorted by water pressure if there is a leak.
Emphatically no regarding relying on the inner seal, it's very thin and only secured by a fairly puny stainless steel band. It serves as a container for any water that leaks in so that the alarm will be immersed.
If your bilge has a lot of water from maybe a leak in the engine cooling raw water system then it's possible that it might have leaked into the alarm void from inside the boat, not through the main diaphragm.
It's also possible that the two wires from the alarm have been damaged by raw water dripping from the exhaust mixer elbow which is directly above the main harness connecting plugs.
If it really is a leaking diaphragm then it is very serious.

[HeinSdL]

Originally Posted by HeinSdL

In your situation I would go to the sensor (starboard side of saildrive, plastic plug with wires coming out at the base of the saildrive) and SLOWLY remove it (careful: use a large set of plyers and protect with a cloth to loosen it. It might be stuck you don't want to break it).

I imagine you have two of these on board, maybe practice taking out the sensor on the other engine first. You will see it's a bit awkward having to twist the lead, and if it's really stuck you can practice getting it out with a pair of plyers (or is it pliers?) and cloth. I subscribe to the view that this is potentially very serious so perhaps should treat the problematic saildrive with a lot of care if not near a place of safety.

[meirriba]

Originally Posted by HeinSdL

......

I would under no circumstances rely on the upper seal to keep the water out on a sustainable basis. I would also not use the engine until the last moment if you discover the lower seal is gone.

Thanks. I do understand why it is dangerous to rely on the inner seal only. What I do wonder about is why you write that operating the engine may cause damage. Aren't the moving parts enclosed in the housing of the seadrive? Or you say that the vibrations may cause a breach of the inner seal?

The sensor is rather stuck so I hesitate to remove it until I will have a spare one on hand so if the old one breaks (and there is water inside) I can put another one in its place.

[HeinSdL]

Originally Posted by meirriba

Thanks. I do understand why it is dangerous to rely on the inner seal only. What I do wonder about is why you write that operating the engine may cause damage. Aren't the moving parts enclosed in the housing of the seadrive? Or you say that the vibrations may cause a breach of the inner seal?

The sensor is rather stuck so I hesitate to remove it until I will have a spare one on hand so if the old one breaks (and there is water inside) I can put another one in its place.

I think the backup/upper seal is not that strong, especially since what's holding it in place are relatively flimsy metal bands. So I am thinking about the vibrations coupled with water pressure from below, could be a bad combo. There are no moving parts. I also read somewhere in a manual to stop the engine when the water ingress alarm comes on.

A pity that sensor is really stuck. Would be good to know quite soon if the lower seal has really failed (catastrophically).

[skipperpete]

Originally Posted by meirriba

Thanks. I do understand why it is dangerous to rely on the inner seal only. What I do wonder about is why you write that operating the engine may cause damage. Aren't the moving parts enclosed in the housing of the seadrive? Or you say that the vibrations may cause a breach of the inner seal?

The sensor is rather stuck so I hesitate to remove it until I will have a spare one on hand so if the old one breaks (and there is water inside) I can put another one in its place.

Check the oil level and quality in the saildrive because there are two separate modes of failure that allow water into the diaphragm void.
The first is a simple failure of the primary diaphragm and they are one tough slab of rubber and rarely give trouble.
The second is the ring of bolts that joins the upper and lower parts of the saildrive, if for some obscure reason these come loose, or are broken/stripped from impact or possibly had the parent metal around them eaten away due to a major electrical leak, water will enter the void and the oil will be milky or it will be replaced by water . If this is the problem and you operate the engine then it's possible to lose the whole lower leg.
In the very worst case scenario you could dive under and stuff the aperture in the hull with maybe the foam rubber from a couple of cushions.

[belizesailor]

False alarms are not uncommon. As suggested above, pull the sensor to confirm before doing anything else.

[meirriba]

Originally Posted by skipperpete

Check the oil level and quality in the saildrive because there are two separate modes of failure that allow water into the diaphragm void.
The first is a simple failure of the primary diaphragm and they are one tough slab of rubber and rarely give trouble.
The second is the ring of bolts that joins the upper and lower parts of the saildrive, if for some obscure reason these come loose, or are broken/stripped from impact or possibly had the parent metal around them eaten away due to a major electrical leak, water will enter the void and the oil will be milky or it will be replaced by water . If this is the problem and you operate the engine then it's possible to lose the whole lower leg.
In the very worst case scenario you could dive under and stuff the aperture in the hull with maybe the foam rubber from a couple of cushions.

Thanks. This was the first check and the oil is fine.

[meirriba]

Originally Posted by belizesailor

False alarms are not uncommon. As suggested above, pull the sensor to confirm before doing anything else.

Update: New sensor obtained.
Old sensor, that I have reported as stuck in place, was removed. What became apparent, that the mechanic that installed it in the factory GLUED the thread! Very silly procedure in my view. Sensor broke of course and the inner thread needs to be cleaned.
To the point: there is water inside between the seals, luckily very little. Anyway we need to take the boat out to replace seals (which we shall do on both seadrives)
One extra comment on the integrity of the upper/inner seal.
To my eyes, it seems very strong (and not puny as referred to in one of the posts). Strong band, held in place by large steel bolts, and as I see it, it holds the seadrive in place. Not that I would advice anyone to ignore Yanmars advice to shut the engine, but I do not think the advice is of die if ignored type...

[HeinSdL]

Ok good to hear nothing too serious. Perhaps update the thread once you know more about the cause of the water entry? Gluing that sensor in place really odd... Otherwise, in my understanding the upper seal has only one function, to keep water out. The saildrive is held in place only by the engine itself and the support at the rear end.

[skipperpete]

You might want to take a closer look at that inner seal, there is only a 5mm wide X ½mm thick band of stainless steel that secures it to a shallow groove in the bolted down flange that mates with and compresses the outer diaphragm. It should never be considered as an alternative to the primary diaphragm.
Having said that, I have never seen a Yanmar main diaphragm fail or tear. Even when a lower saildrive was completely snapped off below after hitting a submerged object in the Malacca straits, the diaphragm remained intact